The umbrella leaves are turning a blackish brown,and dropping off. And the stems are falling off .
Schefflera House Plant
Certified GKH Gardening Expert
This is a severe fungal infection. The most often cause is over-watering. Water only when the top of the soil is completely dry.
To correct the infection, cut off any infected growth just below the infection, and treat the soil with wettable sulfur.
This article will refresh you on the care of these plants: https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm